In order to provide automatic detection of ends of lengths of magnetic tape within a tape handling cartridge system, beginning of tape (BOT) and end-of-tape (EOT) apertures or holes have been formed in the tape. These holes have been sensed optically, e.g. U.S. Pat. Nos. 4,843,490; 4,863,114; and, U.S. Pat. No. 5,327,305; in order to determine cartridge type, tape type, format, etc.
In some tape cartridge systems, such as the one described in U.S. Pat. No. 4,863,114, the tape handling system does not access either the feed reel or the take-up reel, so it is not possible to measure relative rotational velocities at those reels to determine whether a particular hole represents a BOT or EOT aperture. Accordingly, fairly complex patterns of longitudinally and transversely positioned holes have been required to provide for a positive identification of BOT and EOT to the tape handling system.
The BOT and EOT hole patterns are provided by the tape cartridge manufacturer in order to identify the tape thickness, maximum magnetic recording density, coercivity, cartridge type, etc. One reason for differentiating between tape media and cartridges is the continuing trend to increase the coercivity of tape media, while at the same time reducing tape web thicknesses. These variations create the likelihood that a wide variety of cartridge/tape characteristics will be presented to the tape handling system. Before a cartridge tape is formatted and used, the only format information available to the tape handling system comprises BOT and EOT hole sequences. The tape handling system detects the sequences optoelectrically, determines tape/cartridge type from the sequence, and formats and uses the tape/cartridge accordingly.
In the example provided in U.S. Pat. No. 4,863,114, the sequence of holes following an initial BOT or EOT hole was coded to provide a binary code in which "1"s and "0"s were indicated by the presence or absence of holes within the sequence. This arrangement was said to provide a virtually unlimited amount of identification data to the tape handling system. However, it required an extensive and precise tape perforation operation at the time of cartridge assembly. Furthermore, the provision of holes displaced laterally (vertically) as well as longitudinally (horizontally) required a complex optical sensor array capable of sensing holes at various positions across the tape web. Also, the provision of many holes within relatively short segments of the tape tended to result in localized weakening of the tape structurally, leaving it susceptible to stretching or tearing in the event the handling system over-tensioned the tape at the vicinity of the holes.
In the example provided in U.S. Pat. No. 4,843,490, two different tape types were determined based upon sensed distance of a tape-type (TT) hole from a BOT hole. While this system worked well for identifying a few tape types (two types were preferred in the '490 patent), it required precise tape velocity measurement, and no mechanism was provided to verify or qualify the TT hole as being valid, and therefore reliable.
Thus, a hitherto unsolved need has remained for an improved, yet vastly simplified method and arrangement for typing particular tapes and cartridges for use within a tape handling system.